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The two-dimensional two-orbital Hubbard model is studied with the use offinite-size cluster worldline quantum Monte Carlo algorithm. This model iswidely used for simulation of the band structure of FeAs clusters, which arestructure elements of Fe-based high-temperature superconductors. The choice ofa special basis set of hyper-sites allowed to take into account four-fermionoperator terms and to overcome partly the sign problem. Spectral functions andthe density of states for various parameters of the model are obtained in theundoped and low-doped regimes. The correlated distortion of the spectraldensity with the change of doping is observed, and the applicability of the"hard-band" approximation in the doped regime is demonstrated. Profiles of themomentum distribution are obtained for the first Brillouin zone; they havepronounced jump near the Fermi level, which decreases with the growth of thestrength of the interaction. The invariance of the Fermi surface with respectto the strength of the interaction is testified. Nesting is found in the caseof electron and hole doping. Fermi-liquid parameters of the model are derived.Z-factor grows sharply with the increasing the level of doping, andmonotonously decreases with the growth of the strength of the interaction.Moreover, electron-hole doping asymmetry of the Z-factor is revealed. Thenon-Fermi liquid behaviour and the deviation from Luttinger theorem areobserved.

Momentum distribution and non-Fermi liquid behaviour in low-doped two-orbital model: finite-size cluster quantum Monte Carlo approach